It is well established that serum is involved in the regulations of many physiological functions. Recent studies have shown serum also plays an essential role in several important aspects of the neuroimmune mechanism which postulates a communication circuit among the nervous, endocrine and immune systems. Under this mechanism neuropeptides, including those from the pro-opiomelanocortin (POMC) and pro-enkephalin families, are released into the serum by both endocrine glands and immune tissues. These neuropeptides, including ACTH, alpha-MSH, beta-endorphin and Met-enkephalin (MEK), are capable of modulating the activity of circulating immune cells. It is now clear that, apart from being transported to their target tissues, these neuropeptides are also subjected to metabolic processes in the serum which have significant physiological consequences. Serum neuropeptide concentrations are strongly influenced by how they are processed, degraded and whether they are preserved by any protective mechanism. This current project will study these aspects of neuropeptide metabolism in health and stress. It is likely that some serum neuropeptide imbalance related disorders can be traced to perturbation of any or all of these three metabolic processes. Studies will be carried out in five ares in this project 1) Procedures which combine HPLC and capillary electrophoresis with radioimmunoassay will be used to establish serum POMC and MEK peptide levels. This technique will allow accurate measurement of individual peptides by avoiding interference by crossreactivities from related peptides. 2) POMC and MEK peptides will be incubated with serum and the incubation mixture will be analyzed with the aim of defining the patterns of their processing and degradation. 3) Size exclusion chromatography and isoelectric focusing will be used to determine the presence of protective agent(s) for neuropeptides in the serum. 4) Processing and degradation of neuropeptides will be studied with leukocyte membrane preparation and intact cells. 5) All the above studies will be repeated with stressed and unstressed experimental rats to determine if any of the metabolic processes are affected by stress.